No one likes to be compared to someone else. We are all individuals- with different strengths, interests, and abilities. Unfortunately siblings are often compared to one another (purposely or inadvertently). This can create an environment of competition between siblings and sometimes escalates into resentment and fighting. Many parents think the answer to this dilemma is absolute fairness- equal time spent, equal goodies given, etc. But this can be exhausting to calculate and almost impossible to execute.
Treat each of your children as the individuals they are. Show each of your children your unique love for them. Provide encouragement and acknowledge their efforts, feelings, needs, and wishes.